Three simple methods using visual titrimetric,
potentiometric and spectrophotometric techniques are described for the
determination of acyclovir in pure form and in pharmaceutical formulations. The
methods are based on the neutralisation reaction involving the primary amino
group of the drug and acetous perchloric acid in acetic acid medium. In
titrimetric methods, the titration is completed with visual or potentiometric
end-point detection, crystal violet being used as the indicator in visual titration.
In spectrophotometry, the drug is treated with a fixed amount of perchloric
acid-crystal violet mixture and absorbance of the resultant violet colour is
measured at 570 nm and is related to drug concentration. Both titrimetric
methods are applicable over 2-20 mg range of drug and the titration reaction
follows a 1:1 stoichiometry. In spectrophotometry, Beer’s law is obeyed over
the concentration range 5-55 g mL-1
with an apparent molar absorptivity and Sandell sensitivity of 1.78 × 104
L mol-1 cm-1 and 12.68 ng cm-2, respectively.
The limits of detection and quantification are calculated to be 1.696 and 5.654
g mL-1, respectively. The methods were successfully
applied to the determination of acyclovir in tablets. The validity of the
methods was further ascertained by parallel determination by a reference method
and by recovery studies via standard-addition technique.